Admixtures of 2-bromo-2-bromomethylglutaronitrile and a formaldehyde donor

ABSTRACT

The present invention is directed to a synergistic antimicrobial admixture comprising 2-bromo-2-bromomethylglutaronitrile and a formaldehyde donor.

BACKGROUND OF THE INVENTION

U.S. Pat. Nos. 3,833,731; 3,877,922; 3,873,597; 3,644,380; 3,833,743;and 3,929,858 (which are hereby incorporated by reference) disclose2-bromo-2-bromomethylglutaronitrile and its use as an antibacterial,antifungal, and algicidal agent.

Both 3-bromo-2-bromomethylglutaronitrile and a formaldehyde donor areknown individually as antimicrobial agents. The unexpected finding ofthe instant invention is that they are synergistic in combination asantimicrobial agents.

The present invention is directed to synergistic antimicrobialadmixtures comprising 2-bromo-2-bromomethylglutaronitrile (hereinafterreferred to as "BBMG") and a formaldehyde donor.

The present invention is also directed to a method of inhibitingmicrobial growth, comprising contacting said growth with an admixture ofBBMG and a formaldehyde donor.

As used herein, the phrases "antimicrobial" and "inhibiting microbialgrowth" describe the killing of, as well as the inhibition of or controlof the growth of bacteria, yeasts, fungi, and algae. A number ofimportant industries can experience serious adverse effects from theactivity of such bacteria and fungi on the raw materials which theyemploy, on various aspects of their manufacturing activities, or on thefinished products which they produce. Such industries include the paint,wood, textile, cosmetic, leather, tobacco, fur, rope, paper, pulp,plastics, fuel, oil, rubber, and machine industries. Importantapplications of the synergistic antimicrobial combination of the presentinvention include: inhibiting the growth of bacteria and fungi inaqueous paints, adhesives, latex emulsions, and joint cements;preserving wood; preserving cutting oils; controlling slime-producingbacteria and fungi in pulp and paper mills and cooling towers; as aspray or dip treatment for textiles and leather to prevent mold growth;as a component of anti-fouling paints to prevent adherence of foulingorganisms; protecting paint films, especially exterior paints, fromattack by fungi which occurs during weathering of the paint film;protecting processing equipment from slime deposits during manufactureof cane and beet sugar; preventing microorganism buildup and deposits inair washer or scrubber systems and in industrial fresh water supplysystems; controlling microorganism contamination and deposits in oilfield drilling fluids and muds, and in secondary petroleum recoveryprocesses; preventing bacterial and fungal growth in paper coatingprocesses which might adversely affect the quality of the paper coating;controlling bacterial and fungal growth and deposits during themanufacture of various specialty boards, e.g., cardboard and particleboard; preventing sap stain discoloration on freshly cut wood of variouskinds; controlling bacterial and fungal growth in clay and pigmentslurries of various types which are manufactured for later use in papercoating and paint manufacturing for example, and which are susceptibleto degradation by microorganisms during storage and transport; as a hardsurface disinfectant to prevent growth of bacteria and fungi on walls,floors, etc.; and in swimming pools to prevent algae growth. The controlof bacteria and fungi in pulp and paper mill water systems which containaqueous dispersions of papermaking fibers is especially important. Theuncontrolled buildup of slime produced by the accumulation of bacteriaand fungi causes offgrade production, decreased production due to breaksand greater cleanup frequency, increased raw material usage, andincreased maintenance costs. The problem of slime deposits has beenaggravated by the widespread use of closed white water systems in thepaper industry.

Another important area where control of bacterial and fungal growth isvital is in clay and pigment slurries. There slurries are of variousclays, e.g. kaolin, and pigments, e.g. calcium carbonate and titaniumdioxide, and are manufactured usually at a location separate from theend use application, in for example, paper coating and paintmanufacturing, and are then stored and held for later transport to theend use location. Because of the high quality standards for the paperand paint final products in which the slurry is used, it is essentialthat the clay or pigment slurry have a very low microorganism count orcontent so that it is usable in the paper coating or paintmanufacturing.

The synergistic antimicrobial combination of the present invention mayalso be utilized for agricultural and animal health applications, forexample in preventing or minimizing the growth of harmful bacterial,yeast, and/or fungi on plants, trees, fruit, seeds, or soil. Thesynergistic combination is especially useful in treating seed to preventmicroorganism, particularly fungal attack. The synergistic combinationis also useful in protecting animal dip compositions against the buildupof microorganisms, and for this purpose may be combined with aveterinary animal dip parasiticide and an acceptable carrier.

The synergistic combination of the present invention has been foundespecially useful in controlling the harmful effects of microorganismsin water or aqueous media. Systems which utilize circulating water oraqueous media become infected with microorganisms and experiencesubstantial impairment of their efficiency when deposits of themicroorganisms build up in the system. The deposits, called slimes, coatthe walls of tanks and other vessels, and any machinery or processingequipment which is employed, and create blockages in pipes and valves.The slimes also create discolorations and other imperfections in anyproducts being produced, forcing costly shutdowns. Control ofmicroorganisms in aqueous media is particularly important where thereare dispersed particles or fines in the aqueous media, e.g., dispersedcellulosic fibers and dispersed fillers and pigments in papermaking, anddispersed pigments in paint manufacture.

DESCRIPTION OF THE INVENTION

The present invention is directed to a synergistic antimicrobialadmixture comprising 2-bromo-2-bromomethylglutaronitrile (BBMG) and aformaldehyde donor.

The present invention is also directed to a method of inhibitingmicrobial growth, comprising contacting the microbial growth with anadmixture of BBMG and a formaldehyde donor.

Any formaldehyde donor may be used. Examples include2-[(hydroxymethyl)amino]-2-methylpropanol, sold as Troysan 192 by TroyChemical Corporation; 2-hydroxyethyl-2-nitro-1,3-propanediol, sold asTris Nitro by Agnus Chemical Company; blends of5-hydroxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane, sold as Nuosept 95by Nuodex, Inc.; 2[(hydroxymethyl)amino]ethanol, sold as Troysan 174 byTroy Chemical Corporation;1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride, sold asDowicil 100 by Dow Chemical Company; N-(3-chloroallyl)heximiniumchloride; hexamethylenetetramine (hexamine) halohydrocarbonquaternaries, and dimethylol dimethylhydantoin (sold by Glyco Inc.).

The proportions of the two components of the synergistic combination aredictated by the dosage levels of each component, based on 100% activeingredient, which will be employed in each end use application. Therecommended dosage levels are described in detail below.

The synergistic antimicrobial combination active ingredient of theantimicrobial composition of the present invention may be used indiverse formulations: solid, including finely divided powders andgranular materials; as well as liquid, such as solutions, emulsions,suspensions, concentrates, emulsifiable concentrates, slurries and thelike, depending upon the application intended, and the formulation mediadesired. Further, when the synergistic antimicrobial combination isliquid, it may be employed neat or may be incorporated into variousformulations, both solid and liquid, as an adsorbate on suitable inertcarriers such as talc, clays, diatomaceous earth and the like.

Thus, it will be appreciated that the synergistic antimicrobialcombination may be employed to form antimicrobial formulationscontaining the combination as the essential active ingredient, whichformulations may also contain a variety of carrier materials adaptableto industrial and agricultural applications including finely divided dryor liquid diluents, extenders, clays, diatomaceous earth, talc and thelike, or water and various organic liquids such as loweralkanols,kerosene, benzene, toluene and other petroleum distillate fractions ormixtures thereof.

It will be understood also that the synergistic antimicrobialcombination active ingredients may be used in combination with otherantimicrobial materials. For example, the combination can be combinedwith other fungicides and bactericides such as2-(4'-thiazolyl)benzimidazole, sorbic acid, propionic acid, mycostatin,sodium diacetate, trichomycin, amphotericin, griseofulvin, undecylenicacid, esters of parahydroxybenzoic acid, chlorguinaldol,5,7-dichloro-8-hydroxyquinoline, sodium-o-phenylphenate, o-phenylphenol,biphenyl chlorinated phenols, sodium benzoate in appropriateconcentrations and in appropriate instances so as to combine the actionof each to obtain particularly useful results. Such combinations mightfind particular application in the preparation of germicidal soaps, inthe production of cosmetics and aqueous coatings and in combatting papermill slime accumulations. It is quite clear also that the synergisticantimicrobial combination can be combined with other algicidal agentssuch as benzalkonium chlorides and other quaternary ammonium compoundsto obtain formulations particularly suitable to special problems ofalgae control.

In accordance with the present invention there is still further provideda method of inhibiting the growth of at least one of: bacteria, yeast,fungi, and algae, comprising contacting said bacteria, yeast, fungi, oralgae, with a bactericidally, fungicidally, or algicidally effectiveamount of the synergistic antimicrobial combination comprising BBMG anda formaldehyde donor.

The antimicrobial methods of treatment of the present invention involvecontacting the microorganisms involved with the synergisticantimicrobial combination. This can be accomplished either by simpleaddition of the two components of the combination together as a singlecomposition, or by addition of the two components separately. Suchseparate co-administration can either be at the same time or atdifferent times. The net effect will be the same: the article or systembeing treated will ultimately have incorporated therein or have appliedthereto the desired dosage concentration of each component.

As noted above, the instant invention is based upon the discovery thatthe synergistic antimicrobial combination described above is effectivein controlling the growth of bacteria, yeast, fungi and algae in avariety of industrial and agricultural applications. It has been found,for example, that the combination is an effective antimicrobial for thedestruction or control of soil fungi and bacteria and for the protectionof seeds, bulbs and plants. Also, it is an effective algicide in thetreatment of pools and ponds, cooling water systems and the like. Theutility of the synergistic antimicrobial combination of this inventionis shown not only by its activity against bacteria and fungi responsiblefor stunting growth, and even destruction of many types ofcrop-producing plants, but also against those causing degradation anddeterioration of many types of industrial products including, forexample, paper, leather, wood preservation, textiles, aqueous systemssuch as adhesives, resins, drilling fluids, pigment dispersions andlatex paints and oleoresinous coatings whose films are particularlyvulnerable to the destructive action of fungi. The large economic lossesencountered in paper-making operations caused by the accumulation ofbacterial and fungal slimes in various parts of the system can beeliminated to a significant extent by use of the synergistic combinationdescribed herein.

The antimicrobial activity of the compounds described above has beenconfirmed using standard laboratory techniques. They have been foundeffective, for example, in inhibiting bacteria including Aerobacteraerogenes, Pseudomonas species including fluorescens and aeruginosa, andEscherichia coli. They have been found effective also against fungiincluding Penicillium species, Saccharomyces species, Candida species,Fusarium species, and Cephalosporium species. Such bacteria and/or fungicommonly are found on cereal and grain products, in clay and pigmentslurries, on oils, on fruits and vegetables and on cosmetics, leather,electrical insulation, textiles and numerous other materials capable ofsupporting their growth. Also, such bacteria and/or fungi may be foundon plants, seeds, fur and wood and in soils. Further, they may be usedto control overgrowth of algae such as Chlorella sp. including C.pyrenoidosa.

More particularly, the instant compositions may be used when themicrobial growth is selected from the group consisting of Pseudomonasstutzeri, Pseudomonas fluorescens, Pseudomonas aeruginosa, Saccharomycescerevisiae, Aspergillus niger, Penicillium funiculosum, Candida sp.,Fusarium sp., Cephalosporium sp., Trichoderma viride, Cladosporiumherbarum, Aspergillus fumigatus, Pullularia pullulans, Ceratocysticpilifera, Cephaloascus fragrans and mixtures thereof.

As noted above, it has been found that growth of various harmful fungiand bacteria existing in soil is eliminated or limited by use offormulations containing the synergistic antimicrobial combinationdescribed herein. The term "soil" as used here is intended to includeall media capable of supporting growth of plants and may include humus,sand, manure, compost, artificially created plant growth solutions andthe like.

The synergistic antimicrobial combination described above has activityagainst bacteria, yeast, fungi, and algae when employed at appropriatelevels of concentration and may be used to inhibit growth of theseorganisms. It will be obvious to those skilled in the art that therequired effective concentration will vary with particular organisms andin particular applications. In general, however, effective fungicidal,bactericidal and algicidal response is obtained when the synergisticantimicrobial combination is employed in concentrations ranging between10 and 50,000 ppm (parts per million), preferably 100 to 15,000, ppm,most preferably 100 to 500 ppm, of BBMG and between 5 and 10,000 ppm ofa formaldehyde donor, preferably 50 to 10,000, ppm, most preferably 100to 250 ppm, and in a weight ratio of BBMG:formaldehyde donor of 20:1 to1:10, preferably 10:1 to 1:5, most preferably 5:1 to 1:2.5.

Generally, the concentration of formaldehyde donor required forbactericidal activity will be lower than the concentration required forfungicidal activity. The ranges of concentrations recited above reflectthis difference.

For other applications of the type described above, amounts of from0.005 to 0.30% by weight, based on weight of the substrate beingtreated, of the synergistic antimicrobial combination of the presentinvention is incorporated into, sprayed onto, used to dip, or otherwiseapplied to the substrate to be treated in order to prevent growth ofbacteria, fungi, yeasts, and algae.

Following is a table summarizing the dosage ranges for the components ofthe synergistic antimicrobial combination of the present invention invarious types of end uses:

    __________________________________________________________________________                                     Preferred                                                 Concentration (ppm) Ratio                                        Application  BBMG.sup.a                                                                             Formaldehyde Donor                                                                       BBMG:Formaldehyde Donor                      __________________________________________________________________________    Metalworking Fluids                                                                        100-1,000                                                                              200-650    10:1-1:1                                                  pref. 100-500                                                                          pref. 100-500                                                                            pref. 5:1-1:2.5                              Latex Paints and                                                                           100-1,000                                                                              200-650    20:1-1:1                                     Emulsions    pref. 250-500                                                                          pref. 50-2,000                                                                           pref. 10:1-2.5:1                             Clay & Pigment Slurries                                                                    10-250   40-100                                                  Adhesives    100-1,000                                                                              200-650    10:1-1:10                                                 pref. 250-400                                                                          pref. 100-250                                                                            pref. 4:1-1:1                                Paper Coatings                                                                             50-250   40-100                                                  Wood Preservation                                                                          1,000-50,000                                                                           1,900-3,900                                                                              10:1-1:1                                                  pref. 1,900-30,000                                                                     pref. 600-10,000                                                                         pref. 3:1                                    __________________________________________________________________________     .sup.a BBMG = 2bromo-2-bromomethylglutaronitrile                         

Of course, the precise dosages of the components which will be employeddepends upon a number of factors. First, the dosage is indicated inparts per million (ppm), which refers to the concentration of the activeingredient in the environment being treated, for example, theconcentration of BBMG in a clay slurry. This concentration is based on100% active ingredient for convenience in evaluating and comparing testdata. In actual practice, however, various percentages of activeingredient may actually be used, with the balance of the compositionbeing added comprising conventional excipients such as dispersants,stabilizers, preservatives, co-solvents, diluents, and the like.

The components of the synergistic antimicrobial combination of thepresent invention may be added to an article or system to be treated asseparate entities, or as a combination. The two components arephysically and chemically compatible and may be combined simply asactive ingredients, or may additionally be combined with commonlyemployed carriers and excipients, as described above.

The following example, which was actually carried out, will serve tofurther illustrate the present invention, without at the same time,however, constituting any limitation thereof.

EXAMPLES Aqueous Paint and Adhesive

Biocides were added separately and individually to 50 gram aliquots ofthe aqueous paint, latex emulsion, and adhesive as shown in Tables 1through 3. Each aliquot was inoculated with a mixed suspension(approximately 5×10⁶ microorganisms/gram of substrate). The samples wereincubated at 28°-30° C. and were streaked on Sabouraud Maltose agarpetri plates at intervals of 24, 48, 72 hours and seven days afterinoculation. All plates were incubated at 28°-30° C. for seven days. Theresults are reported in Tables I and II.

The microorganisms used in the tests were:

Pseudomonas stutzeri

Pseudomonas fluorescens bacteria

Pseudomonas aeruginosa

Saccharomyces cerevisiae yeast

Aspergillus niger fungi

Penicillium funiculosum

                                      TABLE 1                                     __________________________________________________________________________    Preservation Properties of Combinations of BBMG and                           Formaldehyde Donors in Latex Paint                                                               Test Results at Indicated Intervals                                           Following Microbial Inoculation                            Example                                                                            Amount/Antimicrobial                                                                        24 hr.                                                                             48 hr.                                                                            72 hr.                                                                             7 days                                       __________________________________________________________________________    1    250 ppm Troysan 192.sup.a                                                                   4    4   4    4                                            2    500 ppm Troysan 192                                                                         4    4   4    4                                            3    750 ppm Troysan 192                                                                         4    4   4    4                                            4    1,000 ppm Troysan 192                                                                       4    4   4    4                                            5    2,000 ppm Troysan 192                                                                       4    2   0    0                                            6    250 ppm Tris Nitro.sup.b                                                                    4    4   4    4                                            7    500 ppm Tris Nitro                                                                          4    4   4    4                                            8    750 ppm Tris Nitro                                                                          4    4   4    4                                            9    1,000 ppm Tris Nitro                                                                        4    4   4    4                                            10   2,000 ppm Tris Nitro                                                                        4    0   0    0                                            11   250 ppm Nuosept 95.sup.c                                                                    4    4   4    4                                            12   500 ppm Nuosept 95                                                                          4    4   4    4                                            13   750 ppm Nuosept 95                                                                          4    4   4    4                                            14   1,000 ppm Nuosept 95                                                                        4    2   1    1                                            15   2,000 ppm Nuosept 95                                                                        0    0   0    0                                             .sup.a Troysan 192 (Troy Chemicals Company) = 100% active                     2[(hydroxymethyl)amino]-2-methyl-propanol.                                    .sup.b Tris Nitro (Agnus Chemical Company) = 50%                              2hydroxyethyl-2-nitro-1,3-propanediol and 50% water.                          .sup.c Nuosept 95 (Nuodex, Inc.) = 24.5%                                      5hydroxymethyloxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane, 17.7%            5hydroxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane, 7.8%                      5hydroxypoly[methyleneoxy (74% C.sub.2, 21% C.sub.3 4% C.sub.4, 1%            C.sub.5)]methyl1-aza-3,7-dioxabicyclo(3.3.0)octane, and 50% water.       

    16   250 ppm BBMG  4    4   4    4                                            17   500 ppm BBMG  4    4   4    4                                            18   750 ppm BBMG  4    4   4    4                                            19   1,000 ppm BBMG                                                                              2    1   0    0                                            20   1,500 ppm BBMG                                                                              0    0   0    0                                            21   250 ppm BBMG + 100 ppm                                                                      1    0   0    0                                                 Troysan 192                                                              22   100 ppm BBMG + 100 ppm                                                                      4    4   4    4                                                 Troysan 192                                                              23   100 ppm BBMG + 250 ppm                                                                      4    4   4    4                                                 Troysan 192                                                              24   500 ppm BBMG + 100 ppm                                                                      0    0   0    0                                                 Troysan 192                                                              25   250 ppm BBMG + 100 ppm                                                                      2    0   0    0                                                 Tris Nitro                                                               26   100 ppm BBMG + 100 ppm                                                                      4    4   4    4                                                 Tris Nitro                                                               27   100 ppm BBMG + 250 ppm                                                                      4    4   2    2                                                 Tris Nitro                                                               28   500 ppm BBMG + 100 ppm                                                                      0    0   0    0                                                 Tris Nitro                                                               29   250 ppm BBMG + 100 ppm                                                                      4    4   4    4                                                 Nuosept 95                                                               30   250 ppm BBMG + 250 ppm                                                                      4    2   0    0                                                 Nuosept 95                                                               31   500 ppm BBMG + 250 ppm                                                                      2    0   0    0                                                 Nuosept 95                                                               32   250 ppm BBMG + 500 ppm                                                                      2    2   1    0                                                 Nuosept 95                                                               33   Control-no preservative                                                                     4    4   4    4                                            __________________________________________________________________________     Legend                                                                        4 = Heavy microbial growth                                                    3 = Moderate microbial growth                                                 2 = Light microbial growth                                                    1 = Trace microbial growth                                                    0 = Sterile; no growth                                                        .sup.a Troysan 192 = 100% active                                              [2[(hydroxymethyl)amino]-2-methyl-propanol.                                   .sup.b Tris Nitro = 50% 2hydroxyethyl-2-nitro-1,3-propanediol and 50%         water.                                                                        .sup. c Nuosept 95 = 24.5%                                                    5Hydroxymethoxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane; 17.7%              5Hydroxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane; 7.8%                      5Hydroxy[methyleneoxy (74% C.sub.2, 21% C.sub.3, 4% C.sub.4, 1%               C.sub.5)]methyl 1-aza-3,7-dioxabicyclo(3.3.0)octane, and 50% water.      

                  TABLE 2                                                         ______________________________________                                        Preservation Properties of Combinations of BBMG                               and Formaldehyde Donors in Adhesive                                                           Test Results at Indicated                                                     Intervals Following                                                           Microbial Inoculation                                                               24                                                      Example                                                                              Identification hr.    48 hr.                                                                              72 hr.                                                                              7 days                               ______________________________________                                        1      750 ppm Troysan 192                                                                          4      4     4     4                                    2      1000 ppm Troysan 192                                                                         4      4     4     4                                    3      1500 ppm Troysan 192                                                                         4      4     4     4                                    4      2000 ppm Troysan 192                                                                         4      4     4     4                                    5      3000 ppm Troysan 192                                                                         4      4     3     3                                    6      750 ppm Tris Nitro                                                                           4      4     4     4                                    7      1000 ppm Tris Nitro                                                                          4      4     4     4                                    8      1500 ppm Tris Nitro                                                                          4      4     4     4                                    9      2000 ppm Tris Nitro                                                                          3      3     2     0                                    10     3000 ppm Tris Nitro                                                                          3      0     0     0                                    11     750 ppm Nuosept 95                                                                           4      4     4     4                                    12     1000 ppm Nuosept 95                                                                          4      4     4     4                                    13     1500 ppm Nuosept 95                                                                          4      4     4     4                                    14     2000 ppm Nuosept 95                                                                          4      4     4     4                                    15     3000 ppm Nuosept 95                                                                          4      4     4     4                                    16     100 ppm BBMG   4      4     4     4                                    17     250 ppm BBMG   4      4     4     4                                    18     500 ppm BBMG   4      4     4     4                                    19     750 ppm BBMG   2      2     0     0                                    20     1000 ppm BBMG  1      0     0     0                                    21     250 ppm BBMG + 4      4     3     0                                           100 ppm Troysan 192                                                    22     100 ppm BBMG + 4      4     4     4                                           100 ppm Troysan 192                                                    23     100 ppm BBMG + 4      4     4     4                                           250 ppm Troysan 192                                                    24     400 ppm BBMG + 1      0     0     0                                           100 ppm Troysan 192                                                    25     250 ppm BBMG + 3      0     0     0                                           100 ppm Tris Nitro                                                     26     100 ppm BBMG + 4      4     4     4                                           100 ppm Tris Nitro                                                     27     100 ppm BBMG + 3      2     0     0                                           250 ppm Tris Nitro                                                     28     400 ppm BBMG + 0      0     0     0                                           100 ppm Tris Nitro                                                     29     250 ppm BBMG + 4      4     4     4                                           100 ppm Nuosept 95                                                     30     250 ppm BBMG + 4      4     3     0                                           250 ppm Nuosept 95                                                     31     400 ppm BBMG + 4      2     0     0                                           100 ppm Nuosept 95                                                     32     Control - no preservative                                                                    4      4     4     4                                    ______________________________________                                         Legend                                                                        4 = Heavy microbial growth                                                    3 = Moderate microbial growth                                                 2 = Light microbial growth                                                    1 = Trace microbial growth                                                    0 = Sterile; no growth                                                   

                  TABLE 3                                                         ______________________________________                                        Preservation Properties of Combinations of BBMG                               and Formaldehyde Donors Latex Emulsion                                                            Test Results at Indicated Intervals                       Ex-                 Following Microbial Inoculation                           am-                 .                                                         ple  Identification 24 hr.  48 hr.                                                                              72 hr. 7 days                               ______________________________________                                        1    500 ppm Troysan 192                                                                          4       4     4      4                                    2    1000 ppm Troysan 192                                                                         4       4     4      4                                    3    1500 ppm Troysan 192                                                                         4       4     4      4                                    4    2000 ppm Troysan 192                                                                         1       0     0      0                                    5    750 ppm Nuosept 95                                                                           4       4     4      4                                    6    1000 ppm Nuosept 95                                                                          4       4     4      4                                    7    1500 ppm Nuosept 95                                                                          1       1     1      1                                    8    2000 ppm Nuosept 95                                                                          0       0     0      0                                    9    100 ppm BBMG   4       4     4      4                                    10   250 ppm BBMG   4       4     4      4                                    11   500 ppm BBMG   3       3     3      3                                    12   750 ppm BBMG   0       0     0      0                                    13   100 ppm BBMG + 4       4     4      4                                         100 ppm Troysan 192                                                      14   100 ppm BBMG + 4       4     2      0                                         250 ppm Troysan 192                                                      15   250 ppm BBMG + 4       1     0      0                                         100 ppm Troysan 192                                                      16   250 ppm BBMG + 0       0     0      0                                         250 ppm Troysan 192                                                      17   100 ppm BBMG + 4       4     4      4                                         100 ppm Nuosept 95                                                       18   250 ppm BBMG + 2       0     0      0                                         250 ppm Nuosept 95                                                       19   250 ppm BBMG + 4       4     4      4                                         100 ppm Nuosept 95                                                       20   100 ppm BBMG + 4       4     4      4                                         250 ppm Nuosept 95                                                       21   400 ppm BBMG + 4       1     0      0                                         100 ppm Nuosept 95                                                       22   Latex Emulsion -                                                                             4       4     4      4                                         no biocide                                                               ______________________________________                                         Legend                                                                        4 = Heavy microbial growth                                                    3 = Moderate microbial growth                                                 2 = Light microbial growth                                                    1 = Trace microbial growth                                                    0 = Sterile; no growth                                                   

What is claimed is:
 1. A synergistic antimicrobial admixture comprisingan antimicrobial effective amount of:(a)2-bromo-2-bromoethylglutaronitrile and (b) a formaldehyde donor, whereinthe weight ratio of (a):(b) ranges from about 1:2.5 to about 5:1.
 2. Theadmixture of claim 1, further comprising an inert carrier.
 3. Theadmixture of claim 1, wherein said formaldehyde donor is selected fromthe group consisting of 2-[(hydroxymethyl)amino]-2-methyl-propanol;2-hydroxyethyl-2-nitro-1,3-propanediol; mixtures of5-hydroxymethoxymethyl-1-aza-3,7 dioxabicyclo(3.3.0)octane,5-hydroxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane and5-hydroxypoly(methyleneoxy)methyl-1-aza-3,7-dioxabicyclo(3.3.0)octane;and mixtures thereof.
 4. A method of inhibiting microbial growth,comprising contacting the microbial growth with an effective amount ofan admixture comprising:(a) 2-bromo-2-bromomethylglutaronitrile and (b)a formaldehyde donor, wherein the weight ratio of (a):(b) ranges fromabout 1:2.5 to 5:1.
 5. The method of claim 4, wherein said microbialgrowth is contacted with said admixture as a single composition.
 6. Themethod of claim 4, wherein said microbial growth is contacted separatelywith said 2-bromo-2-bromomethylglutaronitrile and said formaldehydedonor.
 7. The method of claim 4, wherein said microbial growth isselected from the group consisting of Pseudomonas stutzer; Pseudomonasfluorescens, Pseudomonas aeruginosa, Saccharomyces cerevisiae,Aspergillus niger, Penicillium funiculosum, Candida sp., Fusarium sp.,Cephalosporium sp., Trichoderma viride, Cladosporium herbarum,Aspergillus fumigatus, Pullularia pullulans, Ceratocystis pilifera,Cephaloascus fragrans and mixtures thereof.
 8. The method of claim 4,wherein said admixture further comprises an inert carrier.
 9. The methodof claim 4, wherein said formaldehyde donor is selected from the groupconsisting of 2[(hydroxymethyl)amino]-2-methyl-propanol;2-hydroxyethyl-2-nitro-1,3-propanediol; mixtures of5-hydroxymethoxymethyl-1-aza-3,7-dioxabicyclo(3.3.0)octane;5-hydroxymethyl-1-aza 3,7-dioxabicyclo(3.3.0)octane and5-hydroxypoly(methyleneoxy)methyl-1-aza-3,7-dioxabicyclo(3.3.0)octane;and mixtures thereof.